A multivariate path model of genetic and environmental transmission was fitted to specific cognitive abilities data (verbal, spatial, perceptual speed, and visual memory) and evaluated using a maximum-likelihood estimation procedure. In this first multivariate behavioral genetic analysis of adoption data, cultural transmission was modeled via parental phenotypes, each parental phenotype being allowed to affect all traits in the offspring, and assortative mating and cross-assortative mating were accommodated. Results of a preliminary analysis indicated that selective placement is absent in this study. When the full model was fitted to the data, it was found that assortative mating is more important than cross-assortative mating but is substantial only for verbal ability. Genetic transmission parameters are modest in size, whereas cultural transmission is both small and nonsignificant. A simplified model in which cultural transmission and genotype-environment correlation are constrained to be zero provided a good fit to the data. Analyses of the structures of genetic and environmental correlation matrices indicated a strong genetic general factor and a similar, but weaker, environmental factor. Inspection of the genetic transmission parameters suggests that genetic continuity between early childhood and adulthood may be substantial for verbal ability, spatial ability, and perceptual speed.
- cognitive abilities
- path analysis